Particles of cellulose or its derivatives have recently come into use as a chromatographic material. Cellulose or its ion-exchanged products are used as a chromatographic filler. Particularly, a material obtained by introducing ion-exchange groups into a cellulose carrier has the excellent ability to separate proteins, and its utility is evaluated highly.
Intrinsically, a cellulose carrier used as a chromatographic filler is desirably one which is designed sufficiently with regard to the particle size distribution, and the amount and size of pores in the interior. As to the ion-exchanged product, too, it is very important, needless to say, to control not only the amount of ions exchanged but also the amount and size of pores.
Ion-exchanged products of cellulose have already been applied to the separation of proteins and enzymes in the field of biochemistry. Fibrous ion-exchanged cellulose products are widely marketed and generally used. The fibrous cellulose ion-exchanged cellulose products are irregularly shaped, and do not prove to be satisfactory in regard to the elevation of the column pressure when used as a chromatographic filler for filling in a column. To solve this problem, attempts have been made to render the shape of the ion-exchanged cellulose products spherical, and some methods for production thereof have been proposed.
Japanese Patent Publication No. 9712/1973 discloses a method of producing ion-exchanged cellulose particles which comprises dissolving cellulose substituted by ion-exchange groups in an alkaline solvent, emulsifying the solution into small droplets in a water-immiscible solvent, and contacting the emulsion with an acid reactive substance to precipitate the substituted cellulose in the form of spherical porous particles.
Japanese Patent Publication No. 2853/1987 discloses a method of producing particles of an ion-exchanged cellulose product which comprises introducing ion-exchanged groups into solid spherical particles of cellulose while maintaining their solid spherical shape, and then crosslinking the ion-exchanged solid spherical particles of cellulose.
Journal of the Japanese Chemical Society, No. 12, pages 1890-1897, 1981, gives a report entitled the production of spherical ion-exchanged cellulose.
Journal of the Japanese Chemical Society, No. 12, pages 1883-1889, 1981, gives a report entitled the production of spherical cellulose gels and their properties in gel chromatography.
The methods disclosed in the above paper and Japanese Patent Publication No. 2853/1987 involve steps of first producing solid spherical cellulose particles and then crosslinking the cellulose particles. These methods are characteristic in that the solid spherical particles of cellulose are produced by saponifying the granular particles of cellulose acetate, and the crosslinking reaction is carried out in an organic medium.
The affinity separating technique utilizing specific affinitive powder between biological substances has widely been used for the purpose of specifically adsorbing trace substances produced in a biological system and separate and purify them, or removing a specific component from a plasma preparation. Affinitive materials which do not non-specifically adsorb proteins and lipids other than those which are to be treated are suitable as an affinity carrier used for this purpose, and in the past, crosslinked particles of agarose, dextran, and polyacrylamide have been mainly utilized as such. However, since these crosslinked particles have low strength and are limited to use under low pressure conditions, they have the disadvantage of requiring long periods of time for separation. To overcome the disadvantage and perform separation and purification within short periods of time under high pressure conditions, agarose-type carriers having a high degree of crosslinking, polyvinyl alcohol-type carriers and cellulose-type carriers have been developed, but no carrier has yet been developed which is fully satisfactory with respect to all of the amount of ligands introduced, the strength of the carriers and the non-specific adsorption.